We are manufacturing a flex circuit with the following parameters:
1) pad size opening .004, however ther are .025 pads as well.
2) finish - either immersion gold or white tin
3) covercoats - either a flexible soldermask or polyimide covercoats which
we would laser ablate then plasma clean

My questions are as follows:
1) should I be concerned with immersion gold/electroless nickel with a .004
pad feature
2) any known issues with properly developing off the soldermask - right now
we are leaning towards using a Rogers 8080 flexible mask

After building the flex a device is reflowed onto the flex ( on the .004
pads) .005 solder spheres are placed on the device (63/37 tin lead), the
flex is fluxed with Kester TSF6522, device is placed then re-flowed.

Thank you for your comments,
Regards Steve Kelly

PFC Flexible Circuits Ltd.

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